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Full text of "The manufacture and properties of iron and steel"

SWEDEN".                                                 595
but decidedly attractive to the average furnaceman, and it is the foundation of the reputation of Sweden.
Up to the year 1895 Sweden produced more wrought-iron than steel,, but since then the output of iron has remained stationary, while the output of steel has increased. Ninety per cent, of this iron is made on the Swedish Lancashire hearth, an improved form of the ancient device, wherein a mass of pig-iron is caused to melt on the top of a charcoal fire arid the melted mass again brought to the top and remelted, all the time being exposed to the blast, by which the silicon, manganese and carbon are eliminated under the influence of a slag of about the following composition: Si02=10 per cent.; FeO=78 per cent.; Fe203=12 per cent. This gives the softest product that can "be made by any steel or iron-making process, and when a charcoal pig-iron, low in phosphorus, sulphur, manganese and silicon, is used with charcoal, the latter being free from phosphorus and sulphur, the product must necessarily be pure.
In order to get the proper kind of pig-iron, it is necessary to have an ore free from phosphorus. The usual Swedish ore is a hard magnetite; the blast furnaces are small, ranging from 40 to 60 feet in height and 7 to 10 feet bosh, with a diameter at the tuyeres of from 3.5 to 6.5 feet. "When making pig for the Lancashire hearth the blast is kept between 200 0. and 300 0. (390 F. and 570 F.), in order to keep the furnace cool; a diameter of over five feet at the tuyeres is not good practice, for a larger diameter, even with cold blast, will produce so high a temperature that manganese and silicon will be 'reduced. A drawing of a Swedish blast furnace for making pig-iron for the Lancashire hearth is shown in Fig. XXIX-B. The pig-iron used in the. Lancashire hearth runs about as follows, in per cent.:
SI  .............     0.10 to 0.50, usually 0.25 to 0.80
Mn............     0.10 to 0.30
 P..............   ' 0.01 to 0.03
S____..........     0.00 to 0.02
The composition of a very soft Lancashire wrought-iron, used for electrical purposes, is as follows, in per cent.:
c................................    0.05  0.08
SI.V.V *.'.'.'.........................    -023
Mn"........   .....................     O-03
p......................    0.025
g'..............................    0.005